48 



ECHINOIDEA. II. 



The basal part is rather large. In the larger ones the valves join alono- about the onter half. iii smaller 

 ones thev join a longer way down; in the largest specimens seen the head is o-G'"'" long. ~ The 

 ophicephalous pedicellariæ are ver\- pecnliar. One form has an almost globnlar head; the valves (PI 

 IX. Fig. 22) are short and broad, reminding one, indeed, \ery mnch of the ophicephalous pedicellariæ 

 of the Echinijia; the arcs are, however, not distincth" developed, and the stalk is not cnp-shaped. In 

 these features the\- resemble the short broad form of tridentate pedicellariæ in l'rrrJii/nts narcsiainis. 

 and perhaps thev onght really to be regarded as tridentate pedicellariæ. The other form (PL XI. Figs. 

 7, lo) has ver\ elongate, narrow valves, with a terminal widening (the blade); the long narrow part 

 represents the apophysis, whereas the basal part is not distinctly developed. The onter edge of the 

 blade forms a series of large teeth, continning a little \va>' down the sides, rapidh' diminishing in size. 

 There is a simple oval deepening in the widened onter part. One of the valves is considerably longer 

 than the two others, and this one alone has an are de\-eloped below the articular surface. The stalk 

 is cup-shaped above, otherwise compact. The length of the head of these pedicellariæ is ca. i"™, and 

 they are, indeed, verv conspicnous objects, and by no means rare, but thev seem to occur onl\- on the 

 abactinal side, whereas the short, globnlar form seems to occur only on the actinal side. — Regarding 

 the structure of the test of this form, I can only sa>- that the piates are ver\- large and the pores simple. 

 The fossil Cystcchimis crassus described by Gregory (Op. cit) must probably be nearest related 

 to this thick-plated species. Since neither the apical or the actinal system of this fossil form is known, 

 it was perhaps somewhat hazardous to associate it with this genus, as maintained by Agassiz; but 

 when Professor Agassiz savs that the great thickness of the piates.... would seem to preclude the 

 association of this species with Cystccliiinis this objection seems a little curions, since Professor 

 Agassiz himself associates the equally thick-plated form from St. 205 with Cystrchinits — and even 

 includes it in the same species with tlie exceedingly thin-plated form from off Tristan d'Acunha. 



In the fragments of Cysfcchinits clypcatiis from St. 133 and 334, the thin-plated form, I have 

 found four kinds of pedicellariæ, viz. globiferous, tridentate, ophicephalous and triphyllous. The globi- 

 ferous pedicellariæ (PI. IX. Fig. i) are very pecnliar; the blade is an almost closed tube, with a narrow 

 slit along the inner side, and ends in a single hook. I have found only one specimen of this kind of 

 pedicellaria in the dried fragments from St. 133; there is no trace of a thick investing skin, as miglit 

 be expected in a globiferous pedicellaria; I think, however, that it is realh' a globiferous pedicellaria 

 (the only other kind to which it might pos.sibly be referred is the rostrate) '. The tridentate pedi- 

 cellariæ are of two kinds; one has simple, leaf-shaped vahæs (PI. IX. Fig. 20), narrowed only for a 

 short Space below, in the smaller ones joiniug along their whole length; the edge is \ery fineh' serrate. 

 The largest ones seen are ca. o-8""" (head). The other form (PI. IX. Fig. 23) is short, coarse; it was 

 found especially developed in some fragments from St. 133. This form recalls the short thick form of 

 tridentate pedicellariæ of UrccJi. narcsianus, and as all intermediate stages occur between the short, 

 robust form and the long and slender form of tridentate pedicellariæ, it seems to give the proof that 

 this form in UrccJi.iiaresianus must also be regarded as a tridentate pedicellaria. — The small large- 

 headed pedicellaria of Cystech. clypeatus, figured in the Challenger -Echinoidea, PL XLII. Figs. 15 — 16 



I By the name ^rostrate' I designate the kind of pedicellariit nained »die schnabelforniigeii by Doderleiii, as well 

 as those named «die kochloffelformigen > , which are onlj' a modificatioii of the former type, as pointed out by Doderlein; 

 these two forms Professor Doderlein also designates b)' the name laternenformige tridentate pedicellariæ. (Echinoidea d. 

 deutschen Tiefsee-Exp. p. 731. 



